I'm not sure how others feel about this, but I have a diamond reinforced door with a pressure plate. I could use a button, but I prefer pressure plates for convenience.
To test this just have a chicken touch a plate or push a chicken onto a pressure plate. I'm pretty sure this works for any animal and even if the door and pressure plate match. So you can set down a pressure plate in front of a door and then push any animal onto it and it opens. This seems like a security flaw as normally only someone within the citadel group of the door can activate it?
I didn't do much testing though.